1. Field of the Invention
The invention generally relates to a dome valve. More specifically, the invention relates to a dome valve used to selectively dispense a silicon product.
2. Description of the Related Art
The use of valves to dispense a silicon product is known in the art. Typically, a conventional valve, such as a butterfly valve, a ball valve, or a slide gate valve, is coupled to a vessel, which contains the silicon product. The conventional valve is operated between open and closed positions. When the conventional valve is in the open position, the silicon product is dispensed and when the conventional valve is in the closed positions, the silicon product is retained within the vessel. The conventional valve is prone to jamming when particles of the silicon product come into contact with a sealing surface of the conventional valve. More specifically, the silicon particle can become jammed within the conventional valve thereby preventing the conventional valve from operating between the open and closed positions.
Generally, it is desirable to produce the silicon product with a high purity such that contamination of the silicon product by impurities is limited. As such, producing the silicon product with high purity involves careful control of environmental conditions to which the silicon product is subjected. Generally, the conventional valves may introduce impurities to the silicon product because the silicon product contacts the conventional valve. More specifically, the conventional valve is made from a metal, such as stainless steel. The silicon product is abrasive and during operation of the conventional valve, the silicon product can scrape the conventional valve, which results in the separation of the metal of the conventional valve. Exposure of the silicon product to the metal that is separated from the conventional valve can contaminate the silicon product thereby reducing a purity of the silicon product. For silicon products with high purity, contamination levels as low as 1 part per billion atomic (ppba) can influence the utility of the silicon product.
For example, when the conventional valve is coupled to a fluidized bed reactor, the silicon product produced by the fluidized bed reactor comes into direct physical or atmospheric communication with the conventional valves, which can contribute impurities to the silicon product thereby contaminating the silicon product. While methods, such as chemical etching, can be used to surface clean the silicon product to remove surface impurities, these methods add significant processing costs. Thus, contamination of the silicon product should be avoided.
As mentioned above, the conventional valves may become jammed thereby preventing the valve from moving between the open and closed positions. When the conventional valve is coupled to the fluidized bed reactor and becomes jammed, the fluidized bed reactor must be serviced, which increases manufacturing time to produce the silicon product. Moreover, to service the conventional valve, the fluidized bed reactor must be shut down, which results in thermal cycling of components within a reaction chamber of the fluidized bed reactor. Thermal cycling of components within the reaction chamber that are made from graphite and quartz, such as a housing of the reaction chamber, heating elements, and electrodes, can lead to premature breakage of these components. Additionally, when the conventional fluidized bed reactor is serviced, the silicon product that has been produced can become contaminated through interaction with an operator clearing the jammed conventional valve. Accordingly, there remains an opportunity to provide an improved valve for dispensing silicon product from a vessel.